The invention relates to a method of processing a picture signal for conveyance by means of a transmission path or storage medium, said method comprising the steps of:
i) producing a picture signal which corresponds to a picture, PA1 ii) subjecting said picture signal to a segmentation algorithm to produce a region signal which identifies edges and closed regions in said picture, PA1 iii) producing a modified region signal by post-processing the region signal produced in step (ii), and PA1 iv) producing a texture signal which corresponds to the difference between the picture signal produced in step (i) and the modified region signal produced in step (iii). PA1 i) producing a picture signal which corresponds to a picture, PA1 ii) subjecting said picture signal to a segmentation algorithm to produce a region signal which identifies edges and closed regions in said picture, PA1 iii) producing a modified region signal by post processing the region signal produced in step (ii), and PA1 iv) producing a texture signal which corresponds to the difference between the picture signal produced in step (i) and the modified region signal produced in step (iii), PA1 v) producing an appropriate smooth function which is adapted to said region signal, and PA1 vi) adding the function produced in step (v) to said region signal. PA1 i) receiving said region related component and producing a region signal therefrom, PA1 ii) receiving said texture related component and producing a texture signal therefrom, PA1 iii) producing a modified region signal by post-processing the region signal recovered in step (i), and PA1 iv) producing a recovered picture signal by combining said modified region signal produced in step (iii) and said recovered texture signal produced in step (ii) PA1 v) producing an appropriate smooth function which is adapted to said region signal, and PA1 vi) adding the function produced in step (v) to said region signal.
The invention also relates to a method of recovering a picture signal when received in such two component (region and texture) form and apparatus for performing either of the two methods.
Decomposing a picture signal into two components using features identified in the original picture is well known; see for instance "Second-Generation Image-Coding Techniques" by M. Kunt, A. Ikonomopoulos and M. Kocher, Proceedings of the IEEE, volume 73, No. 4, April 1985, pages 549 to 574. The two components then can be coded separately. The reasoning behind this approach is that by finding and encoding perceptually important features of the picture they will be preserved and that by the separation of the picture signal into two components of very different character it is possible to design efficient codes for each of them. Image bandwidth compression aims to reduce the amount of information that must be transmitted while simultaneously preserving the quality of the decoded picture. Region coding schemes so far proposed with good compression tend to be complex. That disclosed in "Region and texture coding of TV pictures" by D. Moran and O. J. Morris, 3rd Intellectual Conference on Image Processing and its Applications (IPA 89), pages 536-540, Warwick, U. K., July 1989 includes post-processing of the region signal prior to the production of the texture signal at the encoder end and similar post-processing of the region signal at the decoder end prior to the reproduction of the picture signal from the recovered region and texture signals. The post-processing involves the adaptive smoothing of false contour edges in the region signal and to achieve this the edges need to be examined to determine whether the contour edge is false or not. In the absence of such determination all edges would be similarly smoothed. Thus such post processing requires false contour detection which adds to its complexity whilst it only operates across a limited number of pixels (one) on either side of a boundary.